Multiaxial Ferroelectricity and Ferroelasticity in a Chiral Perovskite

Organic–inorganic lead-iodide perovskites are attracting tremendous interest because of their great application potential in optoelectronics and photovoltaics. Despite extensive interest, however, no lead-iodide perovskites have been found as multiaxial multiferroic materials with the coexistence of full ferroelectricity and full ferroelasticity. Here, based on the ferroelastic [EQ]PbI3 (EQ = N-ethyl-quinuclidine) with an Aizu notation of 6/mmmF2/m, we introduced a hydroxyl group to N-ethyl-quinuclidine and successfully synthesized a homochiral lead-iodide perovskite multiaxial multiferroic [(R)-N-ethyl-3-quinuclidinol]PbI3 ([R-EQ]PbI3). [R-EQ]PbI3 undergoes a phase transition at 380 K from 622 to 2 point groups, and thereby it is a multiaxial full ferroelectric and also a multiaxial full ferroelastic in the room-temperature phase according to the Aizu notation of 622F2(s). Multiple equivalent ferroelectric/ferroelastic axes can endow [R-EQ]PbI3 with a larger polarization/strain in the polycrystalline samples. This work presents the first multiaxial full multiferroic in lead-iodide perovskites, which would inspire further exploration of chiral perovskite multiferroics for applications such as high precision microdisplacement devices and variable surface acoustic wave delay lines.